Sewage sludge and garbage grinder

ABSTRACT

A sewage sludge grinder comprising a housing, a shaft in the housing, a motor for driving the shaft, a chamber in the housing surrounding the shaft, an outlet and an inlet in the chamber, said shaft being free-ended within said housing and mounting at its terminal portion an assembly comprising an impeller which faces the inlet and tends to move sludge therefrom outwardly radially a set of cutters, and a grid-plate provided with peripheral through slots, the peripheral edge of the impeller cooperating with certain surfaces on said cutters, and the forward face of the grid-plate adjacent said slots cooperating with different surfaces on said cutters, the sludge flowing through the impeller and grid-plate assembly toward the outlet.

United States Patent Burant, Jr.

[451 Apr. 25, 1972 [54] SEWAGE SLUDGE AND GARBAGE GRINDER 52 U.S.Cl. ..24l/46B,24l/46.l1,241/257R 51 Int. Cl. [58] Field of Search ..241/46 A, 46 B, 46.02, 46.1 1,

[56] References Cited UNITED STATES PATENTS 2,012,680 8/1935 l-lammes ..24l/46 B 2,496,359 2/1950 Rymann 3,013,73612/1961 Pontis ..24l/257G Primary Examiner-Granville Y. Custer, Jr. Attorney-Charles R. Fay- [5 7] ABSTRACT A sewage sludge grinder comprising a housing, a shaft in the housing, a motor for driving the shaft, a chamber in the housing surrounding the shaft, an outlet and an inlet in the chamber, said shaft being free-ended within said housing and mounting at its terminal portion an assembly comprising an impeller which faces the inlet and tends to move sludge therefrom outwardly radially a set of cutters, and a grid-plate provided with peripheral through slots, the peripheral edge of the impeller cooperating with certain surfaces on said cutters, and the forward face of the grid-plate adjacent said slots cooperating with different surfaces on said cutters, the sludge flowing through the impeller and grid-plate assembly toward the outlet.

12 Claims, 5 Drawing Figures PATENTEDAPR 2 5 I972 SHEET 2 BF 2 'I/IIIIIIIIIIIIIIIIIIIlI/lllllfl Thermal conditioning has become a widely accepted method for treating sewage sludge prior to dewatering and final disposal. This treatment usually involves passing the sludge through high pressure pumps, heat exchangers and control valves. All of this equipment contains small passages of different kinds which will not pass some of the larger particles normally found in sewage sludge. Consequently, the sludge has to be passed through a grinding device previous to the thermal conditioning to reduce the size of the particles to a maximum which will clear the passages in the thermal conditioning plant. There have been and are presently a number of grinders available for this purpose but each one of them has serious disadvantages, and it is the principal object of the present invention to provide a novel grinder obviating these disadvantages.

Certain of the prior art devices utilize cutting knives and grid-plates which are stationary and such grinders depend mainly upon a shearing action and not to any great extent on impact, and this reliance on shear necessitates accurate and frequent adjustment of the cutting surfaces, and occasional manual removal of retained material is necessary.

Another grinder uses impact to reduce particle size by means of hammers and a circular screen. A great disadvantage if this system is that as certain particles as for instance unground rags pass the hammers, they tend to wrap around and clog the machine. This can be eliminated by increasing the rotation speeds to a point where a high turbulence prevents the accumulation of solids but this high speed requires relatively high power consumption which is excessive.

Other prior art devices utilize knives for a fine comminution I and a mechanical seal to seal in sludge along the shaft. This seal arrangement has been troublesome because grit particles tend to get between the sealing surfaces and wear them out.

SUMMARY OF THE INVENTION In the present invention the grinder may be installed directly in a sludge line as e.g., a 90 elbow in a pipe. Sludge flows into the inlet and impinges against the rotating impeller and grid-plate assembly. The impeller directs the flow towards the outer edge of the grid-plate which has a number of slots along its periphery through which ground sludge passes. The slots in the grid-plate are cut at an angle to the direction of flow so that when it rotates, it imparts a velocity in the direction of flow and thereby acts as a low head pump. When operating at 1,800 R.P.M., this machine will pump water at a rate of I G.P.M. against the static head of 3 to ft. After passing through the grid-plate the sludge flows along a rotating shaft and out through a side outlet.

As the impeller and grid rotate, they pass in close proximity along their outer edges to three hardened steel cutting knives which are equally spaced at 120 from each other. These knives each have two flat surfaces at the tip. One surface wipes along the edge of the impeller, and the other surface wipes along the edge and peripheral face of the grid, thus forming two shearing edges. Large objects in the sludge are first reduced in size by the shearing action between impeller and the respective knife edge, and as these begin to pass through the slots in the edge of the grid-plate they are further reduced in size by shear between the edges of the slots and the respective knife edges. With high rotational speed provided, disintegration is accomplished by impact as well as shear and it is therefore not necessary to maintain close tolerances between the shearing surfaces.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a view in longitudinal section showing the novel grinder;

FIG. 2 is an end view in elevation looking in the direction of arrow 2 in FIG. 1;

FIG. 3 is a view in front elevation of the grid-plate;

FIG. 4 is an edge view thereof, and

FIG. 5 is a front view of the impeller.

PREFERRED EMBODIMENT OF THE INVENTION As shown in FIG. 1, a motor of a size required is indicated at M. This motor has a mounting plate 10 and a shaft 12 passing through a wall 14 of the assembly, the shaft 12 being sealed with respect to a chamber 16 by means of a special packing 18 which however forms no part of the present invention.

Chamber 16 is formed by a pipe or the like 20 having an outlet 22 with mounting flange 24 and by this means is installed directly in a sludge line.

The interior. diameter of the pipe 20 is substantially the same as that of the grid-plate 26 mounted on the shaft 12, as is also the impeller generally indicated at 28. As shown in FIG. 3, the grid-plate 26 is provided with a series of peripherally opening angular slots 30.

Suitably mounted in extension of pipe 20 is a Venturi type reducer generally indicated at 32 being provided with a pipe plug 34 and e.g. three brackets 36, the latter each mounting a threaded rod or bolt member 38 passing through a wall 40 and including nuts 42 by which it may be axially adjusted and locked.

Each bolt 38 mounts a cutter assembly, this being generally indicated at 44, with locking nut 46. The knife 44 is provided with a pair of surfaces 48 and 50, which are generally at right angles to each other, and both providing shearing action. The surface 50 cooperates with the peripheral edge of the impeller, see FIG. 1, and the surface 48 cooperates with the face portions of the slots 30.

There may be as many knife assemblies 44 as desired but it has been found sufficient to have three of these spaced at 120 apart and cooperating as stated with respect to Le, the forward face at the peripheral edge of the grid-plate 26 and the peripheral edge of the impeller.

The inlet is indicated at 52, the sludge first contacting the impeller 28, which has the two radial arms 54 shown. As the impeller and grid-plate assembly rotates, the peripheral edge portions thereof pass in close proximity to the three cutting knives 44. The impeller arms 54 drive the sludge outwardly radially. Large objects are reduced in size by the shearing ac tion between the terminal portions of the impeller arms and the knife edges at 50, and as they begin to pass through the slots 30 at the periphery of the grid-plate, they are further reduced in size by shear between the slot edges and the knife edges at 48. With high rotational speed disintegration is accomplished by impact as well as shear and it is not therefore necessary to maintain close clearances between the shearing surfaces. It is preferable to make the impeller, the grid-plate, and knives of hardened stainless steel.

The present grinder has no rotating or stationary obstruction on the inlet side of the grinding area on which rags and sticks can accumulate. The sludge flow is such that large objects are directed to the peripheral grinding area, thereby averting a build-up of unground objects on the inlet side of the pump, and this makes it possible for the new novel grinder to operate continuously without frequent shut-downs for removal of accumulated unground material.

The cutting knives 44 are installed and adjusted from the outside of the housing and this makes it possible to adjust or replace the knives if necessary without disassembling any parts of the machine.

The present grinder may be installed vertically in a pipe line with inlet 52 at the bottom, so that the sludge flows up towards the grinding area and this will prevent large ungrindable obwith an ordinary water-cooled stuffing box and this is the only practical device for sealing an abrasive slurry such as sewage sludge.

The configuration of the grinder is such that all high turbulence and grinding activity is confined to a relatively small area along the periphery of the rotating impeller and the gridplate, and by confining the turbulence to a small area it is possible to accomplish the disintegration of particles with minimum power consumption.

1 claim:

1. Grinding apparatus comprising a motor driven shaft, a housing therefor, an outlet for the housing, an impeller and grid-plate on the shaft, an inlet for the housing facing the impeller,

and a cutter on the housing, said cutter having a pair of shearing surfaces at an angle to each other, one of said surfaces cooperating with the impeller at the upstream side of the flow of sludge from the inlet to reduce particles in the sludge, the other cutter surface cooperating with the peripheral edge area of the grid-plate, further reducing sludge particles downstream of the flow as regards the impeller.

2. Grinding apparatus of claim 1 wherein the cutter is located at the periphery of the impeller and grid-plate.

3. Grinding apparatus of claim 1 wherein the cutter is located at the periphery of the impeller and grid-plate and the impeller includes radial arms tending to force the sludge outwardly radially toward the cutter.

4. The grinding apparatus of claim 1 wherein said impeller tends to move the sludge radially outwardly, said grid-plate being provided with peripheral slots for passing the sludge.

5. The grinding apparatus of claim 1 wherein said impeller tends to move the sludge radially outwardly, said grid-plate being provided with peripheral slots for passing the sludge and said cooperative grinding with respect to the respective shearing surface of said cutter.

6. The grinding apparatus of claim 1 wherein said impeller tends to move the sludge radially outwardly, said grid-plate being provided with peripheral slots for passing the sludge, said slots being inclined with respect to the axis of said shaft and of said grid-plate and passing completely through the gridplate.

7. Grinding apparatus of claim 1 including means exterior of said housing for mounting said cutter.

8. Grinding apparatus of claim 1 including means exterior of said housing for mounting said cutter, and means for adjusting said cutter.

9. Grinding apparatus of claim 1 including means exterior of said housing for mounting said cutter, and for removing and replacing the same from outside the housing.

10. Grinding apparatus for sludge comprising a housing forming a chamber, a shaft in said housing within the chamber, an inlet for the sludge,

a rotary impeller and grid-plate assembly mounted on said shaft, a plurality of generally radially arranged circumferentially spaced cutters mounted on said housing and projecting inwardly thereof, each cutter having a pair of surfaces at angles to each other,

the impeller including radial arms tending to force the sludge radially outwardly toward the cutters, respective surfaces of each cutter cooperating with the peripheral edge of said impeller arms providing a shearing and grinding action therewith,

the grid-plate having a series of slots therein at the edge thereof, the slots extending through the plate, and the other respective surfaces of the cutters having a shearing and grinding cooperation with respect to the forward face of the grid-plate in the region of said slots, and an outlet, the ground sludge passing through the slots to the outlet.

11. The grinding apparatus of claim 10 wherein the slots are inclined relative to the axis of the shaft and grid-plate.

12. The grinding apparatus of claim 10 wherein the shaft is generally vertical and the inlet is at the bottom of the chamber, the impeller being above the inlet so that heavy ob jects fail to engage the impeller. 

1. Grinding apparatus comprising a motor driven shaft, a housing therefor, an outlet for the housing, an impeller and grid-plate on the shaft, an inlet for the housing facing the impeller, and a cutter on the housing, said cutter having a pair of shearing surfaces at an angle to each other, one of said surfaces cooperating with the impeller at the upstream side of the flow of sludge from the inlet to reduce particles in the sludge, the other cutter surface cooperating with the peripheral edge area of the grid-plate, further reducing sludge particles downstream of the flow as regards the impeller.
 2. Grinding apparatus of claim 1 wherein the cutter is located at the periphery of the impeller and grid-plate.
 3. Grinding apparatus of claim 1 wherein the cutter is located at the periphery of the impeller and grid-plate and the impeller includes radial arms tending to force the sludge outwardly radially toward the cutter.
 4. The grinding apparatus of claim 1 wherein said impeller tends to move the sludge radially outwardly, said grid-plate being provided with peripheral slots for passing the sludge.
 5. The grinding apparatus of claim 1 wherein said impeller tends to move the sludge radially outwardly, said grid-plate being provided with peripheral slots for passing the sludge and said cooperative grinding with respect to the respective shearing surface of said cutter.
 6. The grinding apparatus of claim 1 wherein said impeller tends to move the sludge radially outwardly, said grid-plate being provided with peripheral slots for passing the sludge, said slots being inclined with respect to the axis of said shaft and of said grid-plate and passing completely through the grid-plate.
 7. Grinding apparatus of claim 1 including means exterior of said housing for mounting said cutter.
 8. Grinding apparatus of claim 1 including means exterior of said housing for mounting said cutter, and means for adjusting said cutter.
 9. Grinding apparatus of claim 1 including means exterior of said housing for mounting said cutter, and for removing and replacing the same from outside the housing.
 10. Grinding apparatus for sludge comprising a housiNg forming a chamber, a shaft in said housing within the chamber, an inlet for the sludge, a rotary impeller and grid-plate assembly mounted on said shaft, a plurality of generally radially arranged circumferentially spaced cutters mounted on said housing and projecting inwardly thereof, each cutter having a pair of surfaces at angles to each other, the impeller including radial arms tending to force the sludge radially outwardly toward the cutters, respective surfaces of each cutter cooperating with the peripheral edge of said impeller arms providing a shearing and grinding action therewith, the grid-plate having a series of slots therein at the edge thereof, the slots extending through the plate, and the other respective surfaces of the cutters having a shearing and grinding cooperation with respect to the forward face of the grid-plate in the region of said slots, and an outlet, the ground sludge passing through the slots to the outlet.
 11. The grinding apparatus of claim 10 wherein the slots are inclined relative to the axis of the shaft and grid-plate.
 12. The grinding apparatus of claim 10 wherein the shaft is generally vertical and the inlet is at the bottom of the chamber, the impeller being above the inlet so that heavy objects fail to engage the impeller. 